#41
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US steel trade war
John B. wrote:
One of the problems is that simply welding or brazing two or more pieces together will normally result in some distortion. If it is not a problem, care to elaborate how and when in the process this happens? -- underground experts united http://user.it.uu.se/~embe8573 |
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#42
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US steel trade war
On Mon, 12 Mar 2018 03:59:18 +0100, Emanuel Berg
wrote: John B. wrote: One of the problems is that simply welding or brazing two or more pieces together will normally result in some distortion. If it is not a problem, care to elaborate how and when in the process this happens? Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f This effect is even used to fasten two parts together - a shrink fit. This isn't esoteric information. Every engineer understands it, every welder understands it. You can even see the effect if you have over head high voltage electrical transmission lines, the "sag" of the wires is more on hot days then in freezing weather. -- Cheers, John B. |
#43
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US steel trade war
On Mon, 12 Mar 2018 12:30:04 +0700, John B.
wrote: On Mon, 12 Mar 2018 03:59:18 +0100, Emanuel Berg wrote: John B. wrote: One of the problems is that simply welding or brazing two or more pieces together will normally result in some distortion. If it is not a problem, care to elaborate how and when in the process this happens? Addition to below. "If it is not a problem"? Quite the contrary, it is a problem that occurs in any structure that is exposed to temperature variation. Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f This effect is even used to fasten two parts together - a shrink fit. This isn't esoteric information. Every engineer understands it, every welder understands it. You can even see the effect if you have over head high voltage electrical transmission lines, the "sag" of the wires is more on hot days then in freezing weather. -- Cheers, John B. |
#44
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US steel trade war
John B. wrote:
Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f Still, the area affected is local if we assume two long tubes being put into one so what is distorted is the intersection area (plus change) and by implication the angle or relative positions of the two tubes/tube parts? -- underground experts united http://user.it.uu.se/~embe8573 |
#45
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US steel trade war
On 3/12/2018 8:14 AM, Emanuel Berg wrote:
John B. wrote: Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f Still, the area affected is local if we assume two long tubes being put into one so what is distorted is the intersection area (plus change) and by implication the angle or relative positions of the two tubes/tube parts? In a closed figure, overall expansion/contraction is a real problem. brief review of expansion/warp in welded structures: http://www.lincolnelectric.com/en-us...on-detail.aspx -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#46
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US steel trade war
AMuzi wrote:
In a closed figure, overall expansion/contraction is a real problem. When you see guys do aluminium tubes with MIG or TIG one gets the impression that the filler metal and gas/weld area sure is warm enough but for the whole structure to disalign from this isn't something I instantly think of... I suppose the bicycle frame fixtures have clamps to allow just the right minimal play so that tubes don't suffer too much stress/strain while at the same time still remain in their right places with enough stability? -- underground experts united http://user.it.uu.se/~embe8573 |
#47
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US steel trade war
On 3/12/2018 9:14 AM, Emanuel Berg wrote:
John B. wrote: Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f Still, the area affected is local if we assume two long tubes being put into one so what is distorted is the intersection area (plus change) and by implication the angle or relative positions of the two tubes/tube parts? The very first welding project I ever did was back in the 1970s. I designed and built a little 4' wide, 6'long, 1' deep utility trailer to tow behind our car. The frame is steel angle. Visualize a two horizontal 4' x 6' rectangles of welded steel, with the upper one resting above the lower one on 1' tall vertical steel struts. So after a couple preliminary welding lessons, I welded up the two 4x6 rectangles flat on the workshop floor, then clamped them and the vertical struts together and, working late at night, hurried to weld the verticals. I rushed through the job, then left for home. When I returned the next day, I was very disappointed to see that the trailer "box" was no longer nicely square. The distortion from welding had sort of pulled a rear corner upward an inch or more. I didn't try to correct it, because the trailer was a rush job, and it's plenty strong. There's not much chance of dangerous residual stresses. The trailer's done lots of heavy hauling, and I still use it occasionally. But its not as pretty as I would have liked. -- - Frank Krygowski |
#48
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US steel trade war
On 3/12/2018 1:30 AM, John B. wrote:
On Mon, 12 Mar 2018 03:59:18 +0100, Emanuel Berg wrote: John B. wrote: One of the problems is that simply welding or brazing two or more pieces together will normally result in some distortion. If it is not a problem, care to elaborate how and when in the process this happens? Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f This effect is even used to fasten two parts together - a shrink fit. This isn't esoteric information. Every engineer understands it, every welder understands it. You can even see the effect if you have over head high voltage electrical transmission lines, the "sag" of the wires is more on hot days then in freezing weather. One company I visited once also used the effect to remove distortion. They made big weldments, like the long steel arm brush trimmers that highway departments use to clear plants near roadsides. Those arms are welded up of long steel plates, and usually came out of the welds not very straight. They had guys with big torches who were skilled at "flame straightening," i.e. heating the outside of a bend just the right amount so when it cooled, it pulled the arm straight. -- - Frank Krygowski |
#49
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US steel trade war
On Mon, 12 Mar 2018 14:14:04 +0100, Emanuel Berg
wrote: John B. wrote: Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f Still, the area affected is local if we assume two long tubes being put into one so what is distorted is the intersection area (plus change) and by implication the angle or relative positions of the two tubes/tube parts? In building a bicycle frame one is essentially making two triangles and distortion will have an effect. -- Cheers, John B. |
#50
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US steel trade war
On Mon, 12 Mar 2018 14:14:04 +0100, Emanuel Berg
wrote: John B. wrote: Sure. When you heat, or melt a metal it expands. If you bond two pieces of metal when they are hot, or molten, i.e. in it's expanded state when it cools and shrinks there has to distortion or if the parts are not free to move extreme stress will be imposed. See: https://tinyurl.com/y7feu33f Still, the area affected is local if we assume two long tubes being put into one so what is distorted is the intersection area (plus change) and by implication the angle or relative positions of the two tubes/tube parts? Building a bicycle frame is essentially making two triangles and distortion of any part of a triangle will have rather drastic effects on the triangle. -- Cheers, John B. |
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